Schizophrenia risk factors constitute general risk factors for psychiatric symptoms in the population Elemi J. Breetvelt a,b, ⁎, Marco P.M. Boks a,b , Mattijs E. Numans b , Jean-Paul Selten c , Iris E.C. Sommer a , Diederick E. Grobbee b , René S. Kahn a , Mirjam I. Geerlings b a Rudolf Magnus Institute of Neuroscience, Department of Psychiatry, University Medical Center Utrecht, Utrecht, The Netherlands b Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, The Netherlands c GGZ Leiden en omstreken, The Netherlands article info abstract Article history: Received 17 November 2009 Received in revised form 17 March 2010 Accepted 28 March 2010 Available online 24 April 2010 Background: The presence of a psychosis continuum is suggested by studies showing that schizophrenia and non-clinical psychotic symptoms in the general population share the same risk factors. However, to our knowledge no large-scale studies have been conducted which examine the specificity of these risk factors in the general population. Aim: To investigate whether socio-demographic characteristics associated with non-clinical psychotic symptoms are also associated with other psychiatric symptoms. And secondly, to examine to what extent concomitant psychiatric symptoms explain the relationship between socio-demographic characteristics and non-clinical psychotic symptoms. Methods: In a general population sample of 4894 subjects (mean age 39 years, 45% men) from the Utrecht Health Project we investigated the associations of socio-demographical characteristics with non-clinical psychotic symptoms and other psychiatric symptoms by using the SCL-90. We examined these associations using multivariable logistic regression analyses with and without controlling for the presence of other psychiatric symptoms. Results: Participants with non-clinical psychotic symptoms had an 89% probability of concomitant depressive, anxiety or phobic anxiety symptoms, compared to 11% in participants without psychotic symptoms. The risk profiles for non-clinical psychotic symptoms and other psychiatric symptoms were largely similar. Non-Dutch ethnicity was most strongly associated with non- clinical psychotic symptoms. Adjusting for other psychiatric symptoms did not increase the specificity of the risk factors. Conclusion: Socio-demographic risk factors for non-clinical psychotic symptoms in the general population are also risk factors for other psychiatric symptoms. The relationship between these risk factors and psychotic symptoms are for a substantial part explained by an increase in other psychiatric symptoms. © 2010 Elsevier B.V. All rights reserved. Keywords: Schizophrenia General population Psychotic symptoms Risk factors SCL-90 1. Introduction An important line of research on risk factors for psychotic disorders is the study of non-clinical psychotic symptoms in the general population (Johns, 2005). It is widely accepted that these symptoms are part of a psychosis continuum including schizophrenia (Van Os et al., 2000; Verdoux and Van Os, 2002). This notion is supported by phenomenological similarities (Johns and Van Os, 2001) and the observation that non-clinical psychotic symptoms are more prevalent in relatives of patients with schizophrenia than in the general population (Kendler et al., 1996). Consequently the study of risk factors for non-clinical psychotic symptoms in the general population can provide a Schizophrenia Research 120 (2010) 184–190 ⁎ Corresponding author. UMC-Utrecht, Heidelberglaan 100, 3584 CX Utrecht, PO. Box 85500, 3508 GA Utrecht, HP: B01.206, The Netherlands. Tel.: +31 88 75 56370; fax: +31 88 75 55509. E-mail address: E.J.Breetvelt@umcutrecht.nl (E.J. Breetvelt). 0920-9964/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.schres.2010.03.033 Contents lists available at ScienceDirect Schizophrenia Research journal homepage: www.elsevier.com/locate/schres